The Iola register. [volume] (Iola, Allen County, Kansas) 1875-1902, 1887-05-13

be extended within the compass at the
base of the eye was required. Agreater
length in smaller compass is obtained
by the cord of the main muscle making
an nngle. and the whole action con-
trived to a nicely by the angle. instead
of being round fixed pivot, being
round a loop formed by another muscle.
with the result, that whenever the sec
Ond muscle contracts. it suddenly
witches the first muscle at the point Of
tendon. and thereby produces the rapid
action of the nictitating membrane.
One of the purposes of this men,
brane is. as mentioned. to wash
the eye. In man and some of
his nearest allies. this function is per-
formed by winking the eyelids, and
there is no necessity for any further as
sistance from a third eyelid. In the
same way it is unnecessary in the in-
habitants of the waters. 1t is there
fore absent in the great whale family
and i'm all fishes-the ocean, the river.
or the lake supplying the necessary To-
ton. But there is more than the alb
i sence of this wonderful nictitating
membrane to notice in the eyes of
fishes. for they have no true eyelids at
| all. Skin of structure sufficiently
| transparent to allow of the passage of
the rays of light passes over the eve.
and thus obviates the necessity for
even eyelids. In some cases, as in an
Gel. special protection to the eye is
found-the eel has to work its head
through hard. rough substances such
as gravel and sand. To defend the eye
from injury, therefore, transparent,
horny. convex case is placed be-
fore the eve in sach manner rs
70 defend the organ without imped-
ing the sight = another wonder
full instance of design. The con-
trivances for the protection of the eyes
in the different branches of the animal
world are indeed con slant marvel to
the thoughtful. The nictitating men,
brane is the most conspicuous. and
forms contrast to the singular and
unique arrangement which exists only
i'm the chameleon. Instead of two eve
lids the organ is covered by an eyelid
with Il hole in it, and for an Obvi-
Gus reason. The neck of the chance
leon is infieXible, and to make up for
this. the eye is SO prominent that more
than half the ball projects from the
head. the muscle being such that the
pupil of the eye can be carried in every
direction. To defend and lubricate
the globe of an eye SO unusually ex-
posed, a special continuance was neces-
sary. hence the pierced lid-the lid
itself keeping the principal part of the
surface of the eye under cover and i'm
due state of humidity without con-
slant Meditation, and the aperture al
lowing the necessary admission of
light.
The position of the eyes on the head.
varying. rs it does, the lower we de-
scend in the animal world. affords fur
Their food for reflection In birds and
the higher animals. the position is uni
form. and obviously most beautiful,
symmetrical. and useful: but in fishes
and insects we find an endless variety
as to position. direction and dimensions.
In some fishes, the eyes have an up
ward aspect. and are very close to-
gethcr; in others, they are at the side,
and SO wide apart as to be slightly
downward in direction; whilst in soles,
turbots. founders and others of the
same family. the eyes are placed. as it
were, one above the other, and both
upon the same side of the head. Some
have enormously large eyes; others are
so small as to he scarcely visible; and
others. again. so rudimentary as to be
merely minute fold of the skin on
which cerebral nerve terminates.
Generally speaking. however. the eye of
fishes is large. with especially broad open
pupils; and the crystalline lens much
roundcr than in the eyes of terrestrial
animals-another proof of design. evil
IDENTITY int nded to enable them to col
lect whatever rays of light penetrate to |
the hidden depths of the ocean, rcfrac-
ton of rays of light by more convex
surface being necessity from water |
into the eye. But of all fishes, the |
anableps has perhaps the most note
worthy eye. The creature swinls half |
above the surface of the water. and the |
eye is divided horizontally into two
portions. the one for seeing in the
waite :, the other in the air. Insects.
again. are provided with the most won-
derful organs of sight. Their nature
and construction are different from all
others. and two kinds of eyes. the sim
pie and the composite. are united in
one small creature. The simple eyes
are generally three. and are situated on
the crown of the head between the
more elaborate organs of sight. The
structure of each kind is perfectly
distinct The composite eyes are
a marvellous combination of null
tiplicity of perfect eyes. which
may be seen in microscopic
examination of the cornea. The cornea
then stands revealed as mass of many
thousand regularly disposed hexagonal
facets. each of which is in itself a per-
feet eye. In the head of butterfly.
nearly thirty-five thousand have been
and some insects are suppOs-
ed to be still more numerously sup
piled. The simple eyes. on the other
hand. are simple. as their name inn
plies; each simple eye is single organ
the cornea exhibiting no appearance of
facets. The uses of these eyes, which
the unwearying researches of natural